1. Field of Invention
The present invention relates to an improved cooling system for a transmission clutch package employing a plurality of alternately spaced steel separator plates and friction discs for connecting rotating members in a planetary gear train of an automatic transmission. More specifically, a specialized additional and secondary oil cooling system is described utilizing oil flowing at an accelerated rate for cooling steel clutch plates for conducting heat from the clutch package.
2. Description of Related Art
Generally, the steel separator plates currently used in clutch packages of vehicle transmissions are formed by sheet metal stamping. This produces a flat shaped plate with a thickness of about 2 mm. Anti-rotation lugs are formed around an outer edge periphery. These anti-rotation lugs engage splines of a clutch retainer structure. A plurality of clutch discs are positioned alternately or between the separator plates. The clutch discs have a friction facing material on both sides for contact with an adjacent separator plate. Splines formed on the disc""s inner edge connect the discs to a rotating member or shaft of the transmission. The resultant stack of separator plates and clutch discs are pressed together by a hydraulically powered piston.
An disadvantage of this construction is the steel separator plates are not thick enough to conduct heat rapidly away from the contact surface through the outer lugs and to the clutch retainer. Another disadvantage of this construction is that the whole surface of the steel separator plate which faces the friction material on the clutch disc continuously generates heat. Yet a further disadvantage is caused by the practice of cutting grooves in the friction material to allow oil to flow between the separator plates and the clutch discs which decreases the amount of friction material available for connecting the members together. Still a further disadvantage is caused upon compression of the grooved friction material of the clutch discs which reduces the flow size of oil cooling grooves.
It is an object of the present invention to provide a secondary and additional oil cooling system for a clutch package utilizing oil flow over and along plates of the clutch structure to lower the temperature.
It is another object of the present invention to provide a clutch cooling system including a structure including a laminated plate composite configured to form oil cooling circuits between pairs of plate members for conducting heat always form a clutch package.
It is a still further object of the present invention to provide a separator plate assembly for a clutch package, which is constructed of two identical stamped steel parts.
It is yet another object of the present invention to provide a cooler running clutch package to enhance the life of friction material by reducing the degree of accelerated wear associated with higher temperature.
It is still another object of the present invention to provide an indexing feature on each separator plate to assure positive locating of cooling surfaces when two separator plates are assembled side to side.
It is yet still another object of the present invention provide cooling of the separator plates of a clutch package so as to lower temperatures wherein associated friction surfaces exhibit greater adherence leading to increased efficiency and elimination of at least one clutch disc.
It is a further object of the present invention to reduce the axial length of a transmission by shortening a clutch package which is accomplished by more efficient cooling using oil cooled separator plates and decreasing the number of clutch discs.
It is yet a further object of the present invention to provide a separator plate with strategic oil-cooled channels coined into a face of the plate for cooling oil flow resulting in decreased temperatures and more efficient performance.
To achieve the foregoing objects, the present clutch package has a clutch cooling system using a two-piece steel separator plate assembly using identically formed plate members and with an indexing mechanism to register the two plates together for forming central oil cooled passages resulting in lower operating temperatures.
One advantage of the present invention is that the two-piece steel separator plate assembly is fabricated from a single common stamping.
Still another advantage of the present invention is lower operating temperature as provided by the non-frictional oil cooling surface provided by the two-piece steel separator plate which decreases friction induced wear of the associated frictional surfaces.
A further advantage of the present invention which lowers transmission running temperatures is the increase in frictional effect between the separator plates and clutch discs thereby allowing removal of at least one clutch disc from the clutch package thereby allowing for a shorter transmission which is easier to package in a vehicle.
Yet a further advantage of the present indexed separator plate assembly is a projection formed on the separator plates that assures proper assembly of each pair of plate members into a composite separator assembly.
Yet another advantage of the present invention is providing an increase in oil life by a corresponding decrease in the instantaneous temperature rise of the clutch package occurring at the interface of the frictional material and the steel separator plates during a shift.